This project will study the association between retroviruses, specifically the human T-cell lymphoma/leukemia virus (HTLV), and patients with the acquired immunodeficiency syndrome (AIDS). Serial sera and cellular tissue samples will be obtained from both AIDS patients and those considered to have a prodromal form of the disease. Sera will be assayed for HTLV antigens and for antibodies to HTLV viral or transformed cellular antigens. The specificity of any positive reactivity will be determined by competitive immunofluorescent (IMF), ELISA, and radioimmunoprecipitation (RIP) assays. Further, both fresh and cultured patient T-lymphocytes and monocytes will be analyzed for the presence of HTLV proteins and nucleic acids and for the production of HTLV virions. Techniques employed will include: specific IMF, ELISA, RIP, and reverse transcriptase assays for HTLV proteins; dot blot, Southern and Northern blot, and in situ hybridization assays using cloned and non-cloned HTLV nucleic acid probes; and ferritin-labelled HTLV-specific double antibody electron microscopic assays. Cells so tested will also be evaluated for their phenotypic and functional nature using histochemical stains, monoclonal cell surface markers, and assays for T-lymphocyte helper or suppressor function in order to determine which subclass of T-lymphocytes might be HTLV associated. Lethally irradiated fresh and cultured AIDS cells will be co-cultivated with human and non-human target cell lines to investigate the transmission and isolation of a retrovirus from these patients. Cultured T-lymphocytes from AIDS patients will be immortalized by deliberate infection with HTLV such that cell lines are established and can be examined with specific probes for an AIDS agent in the event that this agent is not completely homologous to HTLV. Virions produced from such transformed AIDS cells will be analyzed for homology to HTLV in the event that infection with parent HTLV rescues a defective retrovirus. Finally fresh and cultured material from AIDS patients will be injected into primates in order to induce an AIDS-like syndrome and the animals will be subsequently analyzed for the presence of HTLV. Elucidation of the etiological agent of AIDS will be an important step in the understanding and eradication of an increasingly lethal public health problem. Understanding the relationship of HTLV or a related retrovirus to a non-neoplastic disease will expand our concept of retroviral toxicity in man.